|Publication number||US5549462 A|
|Application number||US 08/140,397|
|Publication date||Aug 27, 1996|
|Filing date||Oct 25, 1993|
|Priority date||Oct 23, 1992|
|Also published as||DE9215104U1, DE59307641D1, EP0599030A1, EP0599030B1|
|Publication number||08140397, 140397, US 5549462 A, US 5549462A, US-A-5549462, US5549462 A, US5549462A|
|Inventors||Eduard Mischler, Roger Stehr|
|Original Assignee||Maag Pump Systems Ag|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (27), Non-Patent Citations (4), Referenced by (6), Classifications (15), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to a gear pump comprising rotors disposed in roller bearings and its uses.
For compressors, fans, and pumps, particularly screw-type pumps, it is known from U.S. Pat. No. 2,679,412 to support the shaft by means of roller bearings. Between an inner race and a shaft collar on which a pump rotor is supported, an oil throw-off ring arranged directly next to the bearing, a spacer bush, and a sealing counterring, which rests against the shaft collar, are arranged and are clamped together with the inner race to form a subassembly which rotates together with the shaft.
In a bearing housing and sealing housing which encloses this subassembly, two sliding rings are arranged with the same axes between the roller bearing and the sealing counterring and, stressed by springs supported on the housing, rest against the face of the counter ring facing away from the pump rotor. The two sliding rings bound a ring-shaped space, a lubricating fluid pipe leading into this ring-shaped space.
Furthermore, the use of roller bearings for gear pumps is known per se, in which case reference is made, for example, to the following U.S. Patent Documents: ##STR1##
Pumps of this type may be used for the delivery of media at room temperature as well as, as known, for example, from the EP-A 535 295 which was published later, for the delivery of caoutchouc, which takes place at temperatures of from 90° C. to 120° C.
On the whole, the use of externally lubricated roller bearings for the pump rotors has the important advantage that the bearing of the shaft takes place completely independently of the lubricating characteristics of the delivered polymer. Naturally, this requires an absolute separation of roller bearings and delivered media. In addition, roller bearings arranged outside the delivered flow are much more easily accessible for maintenance and servicing purposes than slide bearings situated in the flow of the molten mass, where a demounting is possible only in the hot condition.
It is an object of the present invention to further develop pumps of the initially mentioned type for the delivery of media at high temperatures and to be able to utilize the above-mentioned advantages also in the case of such a use.
For gear pumps, specifically gear pumps which deliver very viscous fluids, such as polymer meltings with differential pressures in the order of up to approximately 500 bar at temperatures >200° C., it has so far been customary to dispose the rotor shafts in slide bearings lubricated by the media.
The above-mentioned object is achieved by the further development of the initially mentioned pump by providing that, for the delivery of very viscous polymer meltings, bearings surfaces of at least one of inner races, outer races of the bearings and bearing surfaces of roller elements are made of a steel with a high-temperature stability.
In contrast to screw-type pumps, in the case of gear pumps, the largest shaft diameter is, as a rule, smaller than the diameter of the root of the tooth of the medium-delivering gearwheels. From this point of view, the inherent stiffness of the shafts is limited. However, any bending of the shafts has the result that the contact conditions of the mating medium-delivering gearwheels as well as the effect of provided shaft sealing devices will be impaired, whereby the service life of the gearwheels and of the shaft bearings will be reduced.
It is therefore particularly astonishing that the arrangement and construction of the bearing according to the invention makes it easily possible to absorb, by means of rotor shafts supported in roller bearings, the above-mentioned stress caused by pressure and particularly also by temperature.
This relates particularly to the delivery of very viscous abrasive media, as, for example, represented by highly filled polymer meltings. In the case of such delivery media and differential pressure of up to 500 bar, a slide bearing lubricated by a delivered medium is subjected to wear which is no longer acceptable economically. A bearing is provided according to the invention which is completely independent of the lubricating characteristics of the delivered polymer. The reason is that the provided roller bearings no longer come in contact with the delivered medium but are lubricated.
In contrast to the customary bearing technology for gear pump rotors, the use of roller bearings is therefore suggested for the above-mentioned rotor shafts. These roller bearings do not come in contact with the delivered medium itself. This permits in an economical manner the use of the gear pump for very viscous abrasive media, such as highly filled polymer meltings.
While it is taken-into account that the temperatures of the melting may be above 300° C., the bearing according to the invention results in economical service lives.
Preferably, the bearing material in the form of S6-5-2 high speed steel or ceramic material such as silicon nitride (Si3 N4) will be used.
In particular, as mentioned above, no external lubricating medium circulating system is provided, but the roller bearings are not lubricated or are lubricated only by lubricant remaining in the bearing. Preferably, a solid-substance lubrication is provided.
Furthermore, in order to minimize the bending of the shafts, the distance between the gearwheel faces and the supporting area of the shaft, determined by the outer contact point in the roller bearing, can be dimensioned to be shorter than determined by twice the median diameter of the shafts along this course.
In particular, when using the gear pump according to the invention for the delivery of a very abrasive delivered medium, such as highly filled plastic masses, one labyrinth seal respectively can be provided between the roller bearing and the gearwheels. As a result, it is prevented, specifically by means of sealing devices, which do not increase the number of components to be provided on the bearing, that delivered medium penetrates from the delivery space into the roller bearings.
Furthermore, as a result of the fact that the labyrinth seals can be tempered by a heat transport medium, the possibility is created to optimize its sealing effect, while taking into account the alternating thermal stress, as caused, for example, by different operating points of the gear pump.
With respect to the construction and the effect of the above-mentioned labyrinth seals, reference is made to "Hydrodynamic Seal for Rotating Shafts", Prof. ret. E. F. Bohn, et al., Chemie-Ingenieur-Technik, 31st Year, 1959, Page 202, an on., as well as to U.S. Pat. No. 4,336,213.
Furthermore, the effect of the labyrinth seal in which the delivery device points from the gearwheels toward the roller bearings is preferred.
A further measure for preventing that delivered medium enters into the roller bearings is implemented by providing, between sealing devices and the roller bearings, an annular gap about the shaft so that possible delivered medium particles penetrating through the seal will fall to the outside through an opening of the gap provided for this purpose.
In the case of such a pump, both pump shafts can be driven separately, for example, by way of an external distributor gear, or only one of the rotors will be driven.
This type of a gear pump according to the invention is particularly suitable for very viscous abrasive media, as represented, for example, by highly filled polymer meltings. Customary fillers and reinforcing materials in this case are, among others, glass fibers, carbon fibers as well as minerals, such as silica sand, ground slate or chalk.
In the following, the invention will be explained by means of a figure.
This FIGURE is a schematic longitudinal sectional view of a gear pump.
In a pump housing 1, two gearwheels 3a and 3b are disposed on two sides respectively on shafts 5a1, 5a2 and 5b1 and 5b2. The shafts and the gearwheel form the rotor.
Since, according to the illustrated embodiment, all rotor shafts are supported in an identical manner, only one shaft with its bearing will be described in the following.
By means of its large-diameter section 9 which is closest to the gearwheel, the shaft 5a1 runs through a labyrinth seal 11 which is constructed in a known manner and whose delivery effect, as known, for example, from the above-mentioned article "Hydrodynamic Seal", as indicated by means of F, preferably points away from the gearwheel 3a.
The labyrinth seal block 13 has a duct or pipe system 15 for a heat transport medium. As a result, the temperature can be influenced in the area of the labyrinth seal 11.
Extending in the axial direction from the seal 11 to the outside, an annular gap 17, following the labyrinth seal block 13, reaches around the large-diameter shaft section 9. The annular gaps 17 of rotor shafts 5a, 5b, which are disposed above one another, communicate, and a fall-out opening 19 is provided which projects downward. Delivered medium, which penetrates through the labyrinth seal 11 axially to the outside, will fall out through the annular gap 17 and farther through opening 19 before it can reach the area of the shaft bearing which will be described in the following.
On the one side, a spacer sleeve 23 which is followed by the inner race 25 of a roller bearing 27 is mounted on the shaft section 21, opposite section 9 with the reduced diameter, which follows the gap 17. The outer race 29 of the roller bearing 27 is fixed in the pump cover 31. Roller elements in the form of bearing cylinders 33 or possibly in the form of bearing balls support the shaft section 21 on the pump cover 31.
For the axial fixing of the inner race 25 on the shaft 5a, a shaft nut 35 is screwed on in an axially connecting manner. Finally, the complete roller bearing 27 is closed off toward the outside by a bearing cover 37.
The bearing surfaces of the inner race 25 and/or the outer race 29 of the bearing and/or of the roller elements 33, preferably all bearing surfaces, consist of a steel of high temperature stability, as, for example, of a high-speed steel S6-5-2 or preferably of a ceramic material, such as silicon nitride Si3 N4.
In particular, in the case of this embodiment with ceramic bearing surfaces, an external lubricating medium circulating system to bearing 27 is omitted. Preferably, a solid-substance lubrication is provided.
Furthermore, for minimizing the bending of the shaft, the distance A between the gearwheel face and the supporting area of the shaft--given by the outer contact point in the roller bearing, is selected to be smaller than twice the median shaft diameter Φ entered in the FIGURE by an interrupted line.
The illustrated gear pump according to the invention with the bearing arrangement according to the invention is particularly suitable for the delivery of very viscous abrasive media, as represented by highly filled polymer meltings. In this case, both rotors may be driven separately by way of an external distributing gear, which is shown schematically at G, or only one of the rotors may be driven.
Thus, one pump may be used in the temperature range of room temperatures of up to above 200° C. and even up to above 300° C.
Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example, and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US1370923 *||Mar 18, 1920||Mar 8, 1921||Ingersoll Rand Co||Independent rotation for percussive tools|
|US1798797 *||Jun 24, 1929||Mar 31, 1931||Jones Philip||Steam control of rotary feeding means|
|US2679412 *||Mar 24, 1950||May 25, 1954||Read Standard Corp||Seal|
|US3131643 *||Oct 25, 1962||May 5, 1964||New York Air Brake Co||Engine|
|US3133506 *||Aug 15, 1961||May 19, 1964||Louis Luciani||Gear pump having internal bearings and seals|
|US3156191 *||Dec 23, 1960||Nov 10, 1964||Clark Equipment Co||Sealing means for pumps and motors|
|US3172366 *||Jul 18, 1961||Mar 9, 1965||Hydro Meca||Hydraulic energy converting device|
|US3309997 *||Jun 2, 1965||Mar 21, 1967||Shimadzu Corp||Gear pump or motor|
|US3473474 *||Nov 1, 1967||Oct 21, 1969||Maag Zahnraeder & Maschinen Ag||Sealing means for high pressure gear pump|
|US3512906 *||Apr 17, 1968||May 19, 1970||Molly Hans||Gear machine|
|US3704968 *||Mar 4, 1970||Dec 5, 1972||Maag Zahnraeder & Maschinen Ag||Gear pump|
|US3746481 *||Aug 6, 1970||Jul 17, 1973||Barmag Barmer Maschf||Gear pump for viscous thermoplastic melts|
|US3830602 *||Mar 14, 1973||Aug 20, 1974||Commercial Shearing||Rotary pumps and motors|
|US4134713 *||Jul 19, 1976||Jan 16, 1979||S.O.M.M.O.S.||Compact fluid driven motor and reduction gear mechanism|
|US4336213 *||Feb 6, 1980||Jun 22, 1982||Fox Steve A||Plastic extrusion apparatus and method|
|US4634300 *||Mar 29, 1985||Jan 6, 1987||Koyo Seiko Company Limited||Rotating member supporting apparatus|
|US4906110 *||Jul 27, 1988||Mar 6, 1990||Balanced Engines, Inc.||Solid-lubricant bearing|
|US5228786 *||Apr 16, 1992||Jul 20, 1993||Koyo Seiko Co., Ltd.||Full type ball bearing for turbochargers|
|DE3922720A1 *||Jul 11, 1989||Jan 18, 1990||Nippon Seiko Kk||Waelzlager|
|DE4125128A1 *||Jul 30, 1991||Feb 13, 1992||Barmag Barmer Maschf||Gear-pump for molten polymer - has screw-thread delivering to interior between unloading zone and airtight seal|
|DE9011156U1 *||Jul 28, 1990||Nov 15, 1990||Schneider, Friedhelm, 5226 Reichshof, De||Title not available|
|EP0028061A1 *||Sep 1, 1980||May 6, 1981||General Signal Corporation||Gear pump or motor|
|EP0158901A1 *||Mar 29, 1985||Oct 23, 1985||Koyo Seiko Co., Ltd.||Rotating member supporting apparatus|
|EP0509218A2 *||Feb 26, 1992||Oct 21, 1992||Paul Troester Maschinenfabrik||Gear pump|
|EP0535295A1 *||Mar 12, 1992||Apr 7, 1993||HERMANN BERSTORFF Maschinenbau GmbH||Device for the treatment of highly viscous rubber or thermoplastic synthetic material|
|JPH01220718A *||Title not available|
|JPH01220719A *||Title not available|
|1||"Introduction To Materials Science For Engineers", by James F. Shackelford, pp. 2-6, Macmillan Publishing Co., 1985.|
|2||"Stahlschlussl", C. W. Wegst, Verlag Stahlschussel Wegst GmbH, 1992.|
|3||*||Introduction To Materials Science For Engineers , by James F. Shackelford, pp. 2 6, Macmillan Publishing Co., 1985.|
|4||*||Stahlschl u ssl , C. W. Wegst, Verlag Stahlsch u ssel Wegst GmbH, 1992.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US6098988 *||Apr 9, 1998||Aug 8, 2000||Honda Giken Kogyo Kabushiki Kaisha||Mechanism for forming a seal around the shaft of a liquid pump|
|US6179594||May 3, 1999||Jan 30, 2001||Dynisco, Inc.||Air-cooled shaft seal|
|US6213745||May 3, 1999||Apr 10, 2001||Dynisco||High-pressure, self-lubricating journal bearings|
|US6264447||Oct 11, 2000||Jul 24, 2001||Dynisco||Air-cooled shaft seal|
|US7495575||Oct 31, 2005||Feb 24, 2009||Saurer Gmbh & Co. Kg||Gear pump|
|US20060120856 *||Oct 31, 2005||Jun 8, 2006||Saurer Gmbh & Co. Kg; Durr Systems Gmbh||Gear pump|
|U.S. Classification||418/1, 384/565, 418/141, 418/206.6, 418/83, 418/179|
|International Classification||F16C33/30, F04C15/00, F01C21/02|
|Cooperative Classification||F04C15/0023, F16C33/30, F01C21/02|
|European Classification||F04C15/00B4, F16C33/30, F01C21/02|
|Dec 21, 1993||AS||Assignment|
Owner name: MAAG PUMP SYSTEMS AG, SWITZERLAND
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MISCHLER, EDUARD;STEHR, ROGER;REEL/FRAME:006829/0628
Effective date: 19931020
|Feb 24, 2000||FPAY||Fee payment|
Year of fee payment: 4
|Mar 17, 2004||REMI||Maintenance fee reminder mailed|
|Aug 27, 2004||LAPS||Lapse for failure to pay maintenance fees|
|Oct 26, 2004||FP||Expired due to failure to pay maintenance fee|
Effective date: 20040827